Re: Dropped fin acks (iptables + lvs)

["Patrik Karén" <patrik.karen@home.se>]

Jan Engelhardt skrev:
>> I am running iptables and lvs on two boxes loadbalancing http[s] and ssh traffic to two real servers.
>> Everything is working just fine from the users point of view. However, 
>> I keep seeing a lot of dropped packets of type ack/fin and ack/rst in 
>> my iptables log. Seems like the connection tracking isn't working the 
>> way I expect it to. The iptables config in short is:
>>     
>
> RST-ACK is received as a response to SYN to a closed port, and hence, is 
> not part of a connection.
>
>   
>> #This is the rule that should allow established connections, right?
>> $IPTABLES -A Firewall-INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
>>     
>
>   
>> Jan 24 16:46:11 10.0.1.107 kernel: drop: IN=eth0 OUT= 
>> MAC=00:15:c5:ee:48:a7:00:04:de:18:18:00:08:00 SRC=<CLIENTIP> 
>> DST=<$VIP1_e> LEN=52 TOS=0x00 PREC=0x00 TTL=49 ID=28407 PROTO=TCP 
>> SPT=48404 DPT=443 WINDOW=65535 RES=0x00 ACK FIN URGP=0
>>     
>
> The FIN-ACK case however looks worth looking into. I'd say do it without 
> -m limit and see if _every_ connection ends up that way. Also use 
> tcpdump to match sessions.
>
>
> 	-`J'
>   
Yes, the FIN-ACKs are the ones that bother me. There are lots of them, 
but I don't know if they occur for every single tcp session.
I'm going to do some tcpdumping tomorrow on different interfaces to see 
if I can find a pattern.

//Patrik